This invention relates to a nuclear fusion reactor comprising a toroidal shell of an electrically conductive metallic material electrically insulated in accordance with a fluidized bed dip coating (which may be abbreviated hereinafter to an "FBC") process with or without an air-core current transformer coil in the form of a toroid electrically insulated in accordance with the FBC process and disposed on the outer peripheral side of the shell. Particularly, the present invention relates to the electrical insulation characteristics of the shell or the shell and the air-core current transformer coil, after the shell or the shell and coil has or have been electrically insulated in accordance with the FBC process.
A conventional nuclear fusion reactor having, for example, a torus shape has comprised a plurality of similar circular coils wound at predetermined equal angular intervals around a toroidal evacuated container of a circular cross section horizontally disposed to establish a toroidal, electrically field within the evacuated container, a toroidal magnetic conductive shell for surrounding the toroidal evacuated container to control the position of a plasma confined within the evacuated container, an air-core current transformer coil in the form of a toroid having a circular cross section disposed on the outer peripheral side of the shell to heat the plasma, and a plurality of vertical and horizontal ports protruding radially of the toroidal evacuated container therefrom and loosely extending through pairs of aligned similar holes disposed in the shell and the coil respectively to observe the plasma confined within the toroidal evacuated container.
The shell and the air-core current transformer coil have generally been electrically insulated by an epoxy resin disposed thereon in accordance with the FBC process. The FBC process, however, is unable to stick the epoxy resin in a layer having a uniform thickness on the surface of each of the shell and coil. The epoxy resin is particularly inclined to stick to the walls of the port holes in the shell and the coil and adjacent portions thereof, and in an extreme case, the port holes might be clogged with the epoxy resin. This has resulted in the necessity of mechanically removing the epoxy resin from the port holes and the adjacent portions and then applying a film or a sheet material such as a polyimide to the exposed walls of the port holes and the exposed adjacent portions. Alternatively, the walls of the port holes and the adjacent portions might be initially applied with such a film or shell material but not electrically insulated in accordance with the FBC process. In recent nuclear fusion reactors operated with high voltages and delivering high outputs, electric discharges have been developed at boundaries between the polyimide films or sheets and the electrically insulating layers of the FBC type disposed on the surface portions adjacent to the port holes of the shell and the air-core current transformer coil and particularly at such boundaries located on the opposite surfaces of the shell and the coil. Those dielectric discharges have frequently resulted in damage to the electrical insulation.
Accordingly, it is an object of the present invention to provide a new and improved nuclear fusion reactor of the type referred to having a high dielectric strength by using electrically insulating insertions to electrically insulate the port holes in the toroidal, electrically conductive shell and the adjacent portions thereof or the port holes in the shell and the air-core current transformer coil and the adjacent portions thereof and to enhance the electrical insulation at boundaries between the electrically insulating insertions and the mating electrically insulating layers of the FBC type.